Our analysis suggests that the early twentieth century warming can best be explained by a combination of warming due to increases in greenhouse gases and natural forcing, some cooling due to other anthropogenic forcings, and a substantial, but not implausible, contribution from internal variability.

Damn that Chief must be a hell of a climber. Even Bruce says 5.12 was just like 5.2 to him. The amazing thing is that he is even better Eco Freak ass kicker.

Anyway getting back to that transition into regional forecasting-WTF, why didn't the industry give us a heads up on this west coast drought?

I have a question for you CAGW geniuses. What conditions of a cool phase PDO causes the sustained high pressure ridge in the eastern pacific off our west coast and how in the hell will CO2 be twisted into causation?

The recent paper by Cowtan and Way (2013), Coverage bias in the HadCRUT4 temperature series and its impact on recent temperature trends, advanced research on global temperature trends by demonstrating (and reducing) a bias in existing temperature indexes.

Incomplete global coverage is a potential source of bias in global temperature reconstructions if the unsampled regions are not uniformly distributed over the planet's surface. The widely used HadCRUT4 dataset covers on average about 84% of the globe over recent decades, with the unsampled regions being concentrated at the poles and over Africa. Three existing reconstructions with near-global coverage are examined, each suggesting that HadCRUT4 is subject to bias due to its treatment of unobserved regions.

Two alternative approaches for reconstructing global temperatures are explored, one based on an optimal interpolation algorithm and the other a hybrid method incorporating additional information from the satellite temperature record. The methods are validated on the basis of their skill at reconstructing omitted sets of observations. Both methods provide superior results than excluding the unsampled regions, with the hybrid method showing particular skill around the regions where no observations are available.

Temperature trends are compared for the hybrid global temperature reconstruction and the raw HadCRUT4 data. The widely quoted trend since 1997 in the hybrid global reconstruction is two and a half times greater than the corresponding trend in the coverage-biased HadCRUT4 data. Coverage bias causes a cool bias in recent temperatures relative to the late 1990s which increases from around 1998 to the present. Trends starting in 1997 or 1998 are particularly biased with respect to the global trend. The issue is exacerbated by the strong El Niño event of 1997-1998, which also tends to suppress trends starting during those years.

Following up on their paper, Cowtan & Way have updated and published their new index using data through December 2013. I thought it would be interesting to compare these new data with the NOAA/NCDC temperature index we have often seen graphed here. To make the two series somewhat more comparable I first re-centered the NOAA data by subtracting monthly means for 1961-1990. Over 1880-2013 (the full run of the NOAA series, although Cowtan & Way go back to 1850), the two look very similar. Their correlation is r = +.97.

20th century warming accelerated in about 1975, and satellite data (UAH and RSS time series) start with 1979, so we often look at this more recent period. Here are NOAA and Cowtan & Way anomalies since 1975. Over this period trends for CW13 are a bit steeper than NOAA (+.18/decade vs. +.16/decade):

Looking at the 1975-2013 graph above you'll notice the two series start to diverge more since about 1999. That coincides with the period when Arctic warming steepened, but Arctic warming is poorly represented in the NOAA and HadCRUT data (a big part of the "coverage bias" CW13 write about).

So here is what it looks like if we restrict analysis just to the past 15 years, 1999-2013. Over this period the CW13 trend (+.13/decade) is almost twice that of NOAA (+.07/decade).